Hydraulic cushion device



Sept. 15, 1964 w. H. PETERSON HYDRAULIC cusHIoN DEVICE 5 Sheets-Sheet lFilled Jan. 29, 1963 Sept. 15, 1964 w. H. PETERSON 3,148,369

HYDRAULIC CUSHION DEVICE Filed Jan. 29, 1965 5 Sheets-Sheet 2 Nw mwsept. 15, 1964 HYDRAULIC CUSHION DEVICE INVENTOR. l WILUAM H. PETERSONNW, mvo; Nm,

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5 Sheets-Sheet 4 Filed Jan. 29, 1963 INVENTOR. WILUAM H. PETERSON Sept.15, 1964 w. H. PETERSON HYDRAULIC CUSHION DEVICE 5 Sheets-Sheet 5 FiledJan. 29, 1963 mail? United States Patent C mce 3,148,869 HYDRAUJECCUSHIN DEVICE William H. Peterson, Homewood, lll., assigner to PullmanIncorporated, Chicago, lll., a corporation of Delaware Filed Ian. Z9,1963, Ser. No. 254,741 Claims. (Ci. 267-1) The present invention relatesto long travel cushion devices and more particularly to an improved longtravel cushion device having a fluid filled cylinder and a iiuiddisplacement means telescopingly arranged therewith and being operativeupon impact to absorb a portion of the kinetic energy of impact.

The hydraulic cushion device of the type to which the improvements ofthe present invention relate is generally disclosed in U.S. Patent No.3,035,827, dated May 22, 1962, assigned to the assignee of the presentinvention. As disclosed in this patent, the cushion unit ischaracterized by a construction which utilizes solely static seals so asto obviate the necessity of dynamic seals' and thereby result in a moretrouble-free and leakproof device.

The unit comprises generally a uid-illed cylinder and a fluiddisplacement means reciprocable therein, the displacement meansincluding a piston head and a hollow piston rod, which upon impact tothe unit contract relatively to each other to displace fluid from oneside of the piston head to the other at a controlled rate of iiow. Therate of flow is controlled by a metering means constructed and arrangedto achieve a substantially constant resisting force during eachincrement of travel of the unit.

For receiving the fluid displaced during the contraction of the unit,there is provided a radially expansible reservoir formed by a flexibleboot which is statically fixed between the cylinder and the hollowpiston rod and in communication with the latter. A resilient returnspring means is disposed between the cylinder and fluid displacementmeans and is operative to return the device to its original extended ornormal position after the shock impact has been dissipated.

The above-described cushion device is primarily adapted for use inrailway cars wherein the lading supporting structure and couplersupporting structure are detached and slidable lengthwise to each other.The cushion device is associated with these relatively slidablestructural components in accordance with my Patent No. 3,003,436 toprovide a controlled acceleration or deceleration of the ladingsupporting structure when impacts are received by the coupler carryingstructure, so that the lading supported thereon is accelerated primarilyby its frictional contact thus maintaining the force between the ladingand its supporting structure at values below that at which damage wouldresult.

Upon relative contracting movement of the cylinder and 4the iiuiddisplacement means, the exible reservoir expands and receives liuiddisplaced during the contracting movement. Conveniently, the iiexiblereservoir is formed from a flexible rubber boot of which the rubber isselected to exhibit substantially uniform strength characteristicsthroughout so as to assure uniform radial expansion of the reservoir ina manner permitting the latter to be accommodated within the limitedspace provided within the device, as well as an allowance for thermalexpansion and contraction. To obtain a rubber boot having the desireduniform strength characteristics requires a rigid quality controlinvolving a time consuming testing of the boots to determine whether theboots fulfill the required standard.

The hydraulic pressures created within the cushion unit can, of course,be quite substantial. Under such circumstances the problem of leakage ofhydraulic fluid is great. improved cushion units, basically of the typedisclosed lih@ atentecl Sept. 15,9 1.964

herein, eliminate the use of dynamic seals toward overcoming thisproblem, but it has remained diiicult to devise a suitable fluid iillingarrangement which meets the leak-proof requirements. In fact, with somedesigns maximum hydraulic pressures developed in the high pressure sideof .the cushion will be in the neighborhood of about 20,000 psi., and itis diicult to provide seals that will not leak at these pressures. Inaccordance with the filling arrangement of the present invention, theneed for such seals is eliminated.

It is a principal object of the present inventions to provide ahydraulic fluid cushion device with ari improved exible reservo-irstructure including a rubber boot and having la reinforcing and/orconfining means constructed and arranged to assure a uniform radialexpansion of the flexible reservo-ir whereby 4the latter may be readilycontrollably accommodated with the space provided therefor.

It is a further object to provide a hydraulic fluid cushion device withan improved reservoir structure including a rubber boot and having areinforcing means which also serves as' a protective shield.

It is another object to provide a hydraulic fluid cushion with animproved arrangement for charging the device with the hydraulic tiuid bylocating seals on the low pressure side ofthe cylinder.

In the drawings:

FIG. 1 is a view partially in section illustrating a hydraulic iiuidcushion unit embodying the improved structure of the present inventionand showing the components in the extended or neutral position.

FIG. 2 is similar to FIG. l but showing the components in the contractedposition thereof.

FIG. 3 is an enlarged fragmentary view of the cushion device partiallyin section showing in particular the improved auxiliary reservoirstructure of the present invention and showing the components thereof inthe extended position of the cushion device.

FIG. 4 is an enlarged fragmentary view of the cushion device partiallyin section showing in particular the improved charging check valvearrangement, this View being taken generally along lines 4--4 of FIG. 1.

FIG. 5 is an enlarged cross-sectional view taken substantially along thelines 5 5 of FIG. l.

FIG. 6 is an enlarged cross-sectional view taken substantially along thelines 6 6 of FIG. 2.

FIG. 7 is an isometric view showing the elastic reinforcing sleeve beingapplied on the rubber casing of the auxiliary reservoir.

FIG. 8 is similar to FIG. 3 but showing the components in the contractedposition of the cushion device.

Referring now -to the figures, there is illustrated a cushion device 10embodying the present invention and including generally a tiuid iilledcylinder 11, a fluid displacement means 12 reciprocable within thecylinder 11, a flexible reservoir in the form of a boot 13 staticallyconnected at one end to the cylinder 11 and at its other end to thetluid displacement means 12, and return spring means 14 disposed betweenthe cylinder 11 and the iiuid displacement means 12.

The cylinder 11 includes generally a tube 16 to one end of which thereis xed a follower or closure plate 17 Disposed inwardly of the other endof the tube 16 is an intermediate cylinder head 18 having an axiallyopening 19. The cylinder head 18 is suitably lixed within the tube 16 bysnap rings 21. A sealing ring 22 is disposed between the contactingsurfaces of the cylinder head 18 and the tube 16 to seal the interior ofthe cylinder from atmosphere.

The uid displacement means 12 includes a piston head 23 reciprocablewithin the bore 24 of the tube 16 and dening on the closure plate sidethereof a high pressure chamber 26 and on the cylinder head side thereofa low pressure chamber 27.

Seated within a groove formed in the periphery of the piston head 23 isa guide and sealing ring 28 which is preferably formed of a laminatedphenolic resin. The guide ring 28 is arranged so that its outer guidingsurface extends above the outer periphery of the piston head 2.3 so asto preclude metal-to-metal Contact between the inner wall of thecylinder bore 24 and the piston head 23.

Fixed to the piston head 23 as by welding is one end of a hollow tubularpiston rod 29 which extends through the axial opening i9 of theintermediate cylinder head l. As shown the outer periphery of the pistonrod 29 and the inner periphery i9 of the cylinder head lll are radiallyspaced from each other and define therebetween an annular space orpassage 3l which provides communication between the low pressure chamber27 and the flexible fluid reservoir i3.

Fixed to the other end of the piston rod 29 is a follower or closureplate 3f.. The closure plate 32 is fixed to the piston rod 29 by meansof a bolt 33 threaded to a plug 34 fixed in the piston rod bore 36. Thebolt 3.3 may be of the type having a plastic insert 3'7 to lock the boltagainst reverse rotation when it has been installed.

As shown in particular in FIG. 4 the threaded opening 3S of the plug 34receiving the bolt 33 communicates with a coaxial passageway 39 oflesser diameter which extends through the other end of the plug 34.Disposed within the passageway .39 is a check valve assembly dllincluding a housing 42 threaded in the inner end of the passageway 39and providing communication between the threaded opening 3S andpassageway 39 by way of an orifice 43. Seated over the orifice d3 is aball check valve i4 biased into seating engagement by a spring 46 whichis retained within the passageway 39 by a retainer housing 47 fixed atits inner end to the valve housing d2.

The cylinder is charged with the hydraulic fluid before the closureplate 32 and bolt 33 are assembled on the piston rod 29 so that thefluid may be introduced through the threaded opening 38, the orifice 43and past the check valve t4 which is unseated by the pressure of theentering fluid and into the piston rod bore 36 via the passageway 39;Fluid flows from the bore 36 into the low pressure chamber 27 via ports@l and into the high pressure chamber 2d via an orifice i9 associatedwith the piston head 23 as more fully to be explained hereinafter. Fluidis also charged into the boot I3 by way of passages 5l. Since cushionlil could be lled standing vertically, passages I permit entrapped airto bleed out, and by squeezing the folded area of the boot, the air hereis freed out insuring a complete fill.

When the unit lll is completely charged, orifice 43 is sealed by anO-ring S2 and plate 53 which are firmly held by a loci; screw Sedisposed in the threaded opening 38. Thereafter the closure plate 32 isfastened to the piston rod 29 by means of the bolt 33 having the plasticinsert 37. The cylinder and the bore of the piston rod 29 are charged tothe extent that in the normal or neutral position of the device shown inFIG. l, the pressure exerted by the fluid is at a minimum, say forexample, about 2 p.s.i. With the above described arrangement of thecheck valve assembly il sealed by the O-ring 52 and sealing plate 53firmly seated over the orifice i3 and the expandable insert 37 in thebolt 33, fluid leakage through the check valve assembly is prevented.The lock screw S4 is formed with a flatted bore to receive a suitabletool for threaded advancement of the lock screw into the threadedopening 3S and into clamping engagement with the sealing plate 53.Similarly, the outer end of the orifice 43 is formed with a flattedsurface to receive a similar tool for ready assembly of the check valveassembly 4l in the plug 34. The arrangement described is ofuncomplicated low cost design, adapted for ready fabrication andinstallation, and includes a multiple arrangement of simple sealingmeans providing for leakproof operation of the cushion unit.

As heretofore described, communication between the high pressure chamber26 and the low pressure chamber 27 is established by way of the pistonhead orifice 49. The orifice 49 extends axially through the piston head22 and merges at one end with a conical feed surface 57 formed on theouter face of the piston head 23.

To obtain a substantially constant resisting force during each incrementof travel of the unit lll from its fully extended neutral position shownin FIG. 1 to its fully compressed position shown in FIG. 2, there isprovided a metering means 58 which serves to meter the rate of flow ofthe fluid through the orifice 49 by varying the effective area thereof.The metering means 53 as shown is in the form of a rod or pin 59slidably extending through the orifice it? and of substantially constantdiameter along its length. The rod or pin 59 is threaded at one endwithin a threaded opening el in the closure plate 17.

Formed along the length of the metering pin 59 are a plurality ofangular spaced flutes 64 each of which vary similarly in cross-sectionso that upon relative movement between the cylinder Il and the fluiddisplacement means l2 the piston head 23 moves along the flutes 64 andthe flow through the orifice 49 at any given distance of travel impartsa substantially constant force-travel characteristic to the cushiondevice. To this end the flutes 64 are designed to conform substantiallywith the relationship wherein AX is the orifice area of any position xover the total nominal stroke d (length of the surface in which theflutes are formed), and AD is the initial orifice area defined by theorifice and the flutes at the beginning of the stroke under conditionswhere a completely rigid body is being cushioned. It is of course to beunderstood that the design of the flutes may be varied somewhat from theabove relationship to achieve the desired constant force travelcharacteristics for any given situation. For a more completedescription, reference is made to the aforementioned US. Patents3,003,436 and 3,035,827.

Fixed on and located outwardly of the ports 48 of the piston rod 29 is astop ring 66 which, as shown in FIG. l, engages the cylinder head 18 tolimit the travel of the fluid displacement means l2 to its fullyextended position. This provides a minimum low pressure volume in thelow pressure chamber 27 for receiving the fluid from the chamber 26 viathe orifice 4% and bore 36 of the piston rod 29.

The flexible reservoir or boot chamber 13 further extends the lowpressure chamber 27 and, as shown in FIGS. 3 and 5 8, includes a casing67 formed from a fluid impervious, flexible material capable ofresisting any corrosive effects that the hydraulic fluid may have.Advantageously, the material may be a type of rubber having specialadditives for low temperature flexibility.

The thickness of the rubber boot 67 is selected so as to provide thegreatest strength and ruggedness commensurate with the flexibilityrequired and may be, for example, 3/16 inch. As shown in FIGS. 3 and 8,the boot 67 is flexed between `the neutral or deflated position shown inFIG. 3 wherein the reservoir is devoid of any substantial quantity offluid to an expanded position shown in FIG. 8 wherein it accommodatesthe fluid displaced during contraction of the unit. The rubber boot 67may, when being filled by the displaced fluid, tend to bulge inlocalized areas in the nature of a bubble such that the boot cannot beaccommodated wholly within the boot chamber 63 defined by the open endof the cylinder tube 16 outwardly of the cylinder head 18, yand thenormal smooth folding action interfered with. This may causemalfunctioning of the cushion device 10 or may even cause the boot 67 tobe pinched between the cylinder end and the closure plate 32 so as tocause the latter to be ruptured. The tendency of the rubber boot 68 tobubble may be inherently caused by such as variations in the boot wallthickness or variations in the curing properties and the like.

In accordance with the present invention there is provided a reinforcingmeans which controls and serves to prevent the non-uniform expansion ofthe rubber boot 67 and assures that the expanded boot is maintainedwithin the confines of the boot chamber 68. This is accomplished by theuse of pliable reinforcing means 69 overlying the exterior of the boot.The pliable reinforcing means 69 is constructed and arranged so as tocontrol and maintain a substantially uniform radial expansion of theboot casing while precluding substantially any longitudinal expansion.To this end there is employed a pliable fabric in the form of a seamlesssleeve capable of radial stretching or expansion, as ditinguished from auniversal stretch, in the nature of a two-way stretch, while beingincapable of any substantial longitudinal elongation. The pliable fabricis preferably formed from threads produced from synthetic yarns and mayinclude kinked yarn or elastomers arranged to provide the radialexpansion. The pliable fabric having the desired elastic characteristicsmay be braided, woven, or knitted.

The elastic fabric sleeve 69 is sized such that it is stretched over theboot casing 67 as shown in FIG. 7 so as to be partially radiallyextended or expanded. However, upon radial expansion of the boot betweenthe positions shown in FIGS. 3 and 8, the sleeve 69 further expands andapplies a peripherally uniform resisting force against the underlyingrubber boot casing 67. It is to be noted that as the boot casing 67expands, the reversed end portion 71 fixed to the piston rod 29 curlsoutwardly along the piston rod and is wholly confined within the bootchamber 68. Such curling of the reversed end is permitted by theflexibility of the casing material and the pliability of the sleeve 69.However, because the sleeve is constructed to prevent any substantiallongitudinal extension of the boot casing 67, any outward bulging of theboot is substantially precluded.

In the fully expanded position the elastic sleeve 69 is completelyextended so that it applies a force resisting further radial expansionof the underlying boot 67. The sleeve 69 is constructed so as tomaintain the maximum outer diameter of the expanded boot casing 67somewhat less than the maximum diameter of the boot chamber 68. In thismanner a clearance space is provided between the boot 13 and thecylinder tube 16 whereby any seizure of the boot within the cylinder isprevented.

It is further noted that the elastic sleeve or sheath 69 particularlywhen formed of synthetic yarns serves as a protecting shield for thesoft underlying rubber boot 67 and protects the latter against abrasion,scoring, cutting and the like.

The boot assembly including the rubber boot casing 67 and the overlyingelastic fabric sleeve 69 is fixed at one end to a hub 72 of theintermediate cylinder head 18 by way of a suitable hose clamp 73. Theother end of the boot casing 67 preferably projects from the sleeve 69and is separately fixed by a clamp 74 to the piston rod 29 to establisha fluid seal therewith. The other end of the sleeve 69 is fixed with anoverlying portion of the boot casing 67 to the piston rod by anotherclamp 75. The sleeve 69 is fixed tautly between the clamped ends so asto be capable of providing the longitudinal reinforcement describedabove which at the same time permitting the boot casing 67 to expand.

Assuming that the cushion device 16 is assembled to the extent that theclosure plate 32 and spring 14 are not mounted thereto, the hydraulicfluid is charged into the unit via the charging check valve assembly 41.The fluid fills the cylinder 11, piston rod bore 36 and the auxiliaryreservoir of the boot 13 via the various communicating openings such asthe ports 48, annular opening 31 and orifice 49, as heretoforedescribed.

Assuming further that the cushion device 19 is employed in a railway Carbetween the lading supporting and coupler mounting structures to isolatethe shock from the lading, the components of the device assume theposition illustrated in FIG. 1 in the absence of shock impact at thecouplers. Upon shock impact in either buff or draft, the cylinder 11 andthe piston head 23 move relatively to each other toward the compressedor contracted position of the device illustrated in FIG. 2.

As the cushioning device contracts under the impact or force beingcushioned, the metering pin 59 displaces hydraulic fluid containedwithin piston bore 36 through the ports 43 into the low pressure chamber27 and through the annular opening 31 into the boot or reservoir 13,causing the latter to expand. In the event the rubber has localized weakareas, there may be a tendency for the latter to bulge or form abubble-like projection during the filling thereof. As heretoforedescribed, the elastic fabric sleeve 69 which is prestretched exerts acounteracting inner radial force which precludes such localized bulging,but yields readily under the pressures within the boot chamber to permitexpansion thereof to the limit, but beyond this point, the fabric exertsa sharp increase in force, thus preventing further radial expansion,shown in FIG. 8. At the same time, the longitudinal confining forceexerted by the fabric sleeve 69 substantially prevents any elongation ofthe boot casing 67.

The hydraulic ilow initiated by the relative movement of the piston head23 and the cylinder 11 is directed from the high pressure chamber 26 totthe low pressure chamber 27 via the orifice 49, to the piston rod bore36 and ports 48 land thence into the boot reservoir 13. The rate of flowthrough the orifice 49 is controlled by way of the metering pin 59 andthe flutes 64 formed thereon so as to vary the effective orifice areasuch that the resisting force is maintained substantially constant foreach increment of travel of the components. Contraction of the unit 19continues until the open end o-f the cylinder contacts the closure plate32. After the shock has been fully dissipated the return spring 14 isoperative toy return the hydraulic cushion components to` the initialextended position yas limited by contact of the stop ring 66 with thecylinder head 18. During this movement under the action of the spring14, the oil flow previously described is reversed and the boot reservoir13 deflates and returns to the position shown .in FIGS. l and 3, therebyinsuring that the hydraulic fluid displaced by the piston is restored toits normal position.

What is claimed is:

1. A hydraulic cushion device comprising a fluid-filled cylinder havinga closed end and an open end, fluid displacement means reciprocablyreceived by said cylinder for rel-ative movement between a neutralextended position and `a contracted position, an intermediate cylinderhead fixed in said cylinder inwardly of said open end, an axial openingin said cylinder head, said fluid displacement means including a pistonhead reciprocal within said cylinder between said closed end and saidintermediate cylinder head and defining adjacent the closed end-sidethereof a high-pressure chamber and adjacent the intermediate sidethereof a low-pressure chamber, a piston rod fixed to said piston headand extending through said intermediate cylinder head opening, fluidpassage means through said intermediate cylinder head, said fluiddisplacement means including means providing fluid communication betweensaid high-pressure chamber and said low-pressure chamber duringcontraction and extension of said device, a flexible auxiliary reservoirfixed at one end yto said piston rod and at the other end to saidintermediate cylinder head and communicating with said low-pressurechamber by way of said fluid passage means, said flexible reserviorbeing expandable for receiving fluid displaced upon relative contractionof said fluid displacement means and said cylinder, said flexiblereservoir including a rubber boot and an overlying sleeve means forcontrolling the expansion of said rubber boot, said sleeve means in thedeflated condition being partially expanded and tensioned on said rubberboot and in the fully examasar;

panded condition exhibiting a diameter less than the diameter of saidcylinder so as to maintain a clearance between said flexible reservoir`and the inner surface of said cylinder.

2. The invention as defined in claim 1 wherein said sleeve means issubstantially incapable of elongation so that said boot is substantiallyonly radially expanded and is maintained within the contines of the openend of said cylinder and said intermediate cylinder head in the maximumexpanded condition thereof.

3. In a hydraulic cushion device wherein uid iilled cylinder and pistonmeans telescopically coact to absorb forces -applied thereto, at leastone of said cylinder and piston means `being formed with a tubularportion closed off at one end thereof by .a removable end plate, theprovision of -a Huid charging and end plate -attachment unit forming apart of said one cylinder and piston means, said unit comprising plugmeans xed in said tubular portion, a fluid delivery passage extendingthrough said plug means, said passage including a threaded portion,check valve means in an innermost portion of said passage and operativeto permit one-Way ow of fluid during charging of said cushioning device,and end plate fastener means extending through said end plate andthreadedly received in said threaded pontion of said passage.

4. The device of claim 3 wherein said check valve means includes a Valveseat portion threadedly received in said passage, said valve sea-tportion being provided with a iuid ow orifice coaxial with said passageand formed with tool engaging surfaces for blind insertion and removalof said check valve means.

5. The device of claim 3 wherein sealing means are received in thethreaded portion of said passage between said check valve means and saidfastener means, said sealing means including an imperforate discperipherally mounting Ian O-ring in a recessed seating area, Iand locknut means threadedly received in said passage and engaging said disc andpressing said O-ring into sealing engagement with a radial surfaceportion of said passage, said lock nut means including tool engagingmeans for blind insertion and removal thereof.

References Cited in the file of this patent UNITED STATES PATENTS635,848 Dutton Oct. 31, 1899 2,643,112 Smith June 23, 1953 2,725,078Glancy Nov. 29, 1955 3,003,436 Peterson Oct. 10, 1961 3,035,714 PetersonMay 20, 1962

3. IN A HYDRAULIC CUSHION DEVICE WHEREIN FLUID FILLED CYLINDER ANDPISTON MEANS TELESCOPICALLY COACT TO ABSORB FORCES APPLIED THERETO, ATLEAST ONE OF SAID CYLINDER AND PISTON MEANS BEING FORMED WITH A TUBULARPORTION CLOSED OFF AT ONE END THEREOF BY A REMOVABLE END PLATE, THEPROVISION OF A FLUID CHARGING AND END PLATE ATTACHMENT UNIT FORMING APART OF SAID ONE CYLINDER AND PISTON MEANS, SAID UNIT COMPRISING PLUGMEANS FIXED IN SAID TUBULAR PORTION, A FLUID DELIVERY PASSAGE EXTENDINGTHROUGH SAID PLUG MEANS, SAID PASSAGE INCLUDING A THREADED PORTION,CHECK VALVE MEANS IN AN INNERMOST PORTION OF SAID PASSAGE AND OPERATIVETO PERMIT ONE-WAY FLOW OF FLUID DURING CHARGING OF SAID CUSHIONINGDEVICE, AND END PLATE FASTENER MEANS EXTENDING THROUGH SAID END PLATEAND THREADEDLY RECEIVED IN SAID THREADED PORTION OF SAID PASSAGE.